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authorVladimir Zapolskiy <vladimir_zapolskiy@mentor.com>2015-05-18 20:11:46 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-06-01 06:38:21 +0900
commitb575f7124ab33b2a4239613bcc870380308fe0a7 (patch)
treeb8b35a0f055588f9e2f4361c601d8e01bc64c52d /drivers/char
parentb144ce2d37619e05afdb0a15676500d76a64b1be (diff)
downloadlinux-b575f7124ab33b2a4239613bcc870380308fe0a7.tar.bz2
char: misc: restore MISC_DYNAMIC_MINOR on device_create() failure
On attempt to register a dynamic minor misc device its minor number is updated to a virtual minor number prior to device_create() call, however on error path misc->minor == MISC_DYNAMIC_MINOR is not restored. Following the rule of thumb that a function returning an error must not change the state of the caller, assign MISC_DYNAMIC_MINOR back. The problem is met in a sutuation, when subsys_initcall(misc_init) is not yet called and misc_class is not created, but misc_register() modifies statically defined ".minor = MISC_DYNAMIC_MINOR", therefore implicitly changing the client's logic on next attempt (e.g. retrying from deferred list) to register a misc device, whose minor number is converted from dynamic to some unknown static one. Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/misc.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index a4d3674e3277..fdb0f9b3fe45 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -186,12 +186,13 @@ int misc_register(struct miscdevice * misc)
{
dev_t dev;
int err = 0;
+ bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
INIT_LIST_HEAD(&misc->list);
mutex_lock(&misc_mtx);
- if (misc->minor == MISC_DYNAMIC_MINOR) {
+ if (is_dynamic) {
int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
if (i >= DYNAMIC_MINORS) {
err = -EBUSY;
@@ -216,9 +217,13 @@ int misc_register(struct miscdevice * misc)
device_create_with_groups(misc_class, misc->parent, dev,
misc, misc->groups, "%s", misc->name);
if (IS_ERR(misc->this_device)) {
- int i = DYNAMIC_MINORS - misc->minor - 1;
- if (i < DYNAMIC_MINORS && i >= 0)
- clear_bit(i, misc_minors);
+ if (is_dynamic) {
+ int i = DYNAMIC_MINORS - misc->minor - 1;
+
+ if (i < DYNAMIC_MINORS && i >= 0)
+ clear_bit(i, misc_minors);
+ misc->minor = MISC_DYNAMIC_MINOR;
+ }
err = PTR_ERR(misc->this_device);
goto out;
}